systemd has supported timer units for activating services based on time since its inception. However, it only could schedule services based on monotonic time events (i.e. "every 5 minutes"). With this feature in place systemd also supports calendar time events (i.e. "every monday morning 6:00 am", or "at midnight on every 1st, 2nd, 3rd of each month if that's saturday or sunday").

In timer units you may now use OnCalendar= to express a calendar time event. The syntax is quite flexible and in some ways more powerful than cron's (and certainly more readable). For a more detailed discussion of the syntax see the documentation.